A power shovel is well known as an excavation machine capable of excavating and loading earth and sand. Generally, a power shovel generates hydraulic pressure by a hydraulic pressure pump driven by a diesel engine so as to carry out all the operation of a run and a work. Further, a crawler type travel gear is widely used as a travel gear. As for a basic structure of a power shovel, the power shovel includes a self-propelling lower traveling body and an upper rotation body capable of rotating 360 degrees on the lower traveling body. When the upper rotation body faces toward a running direction, a driver seat and a working device are provided at a front section of the upper rotation body, and a power source such as an engine or the like is provided at the rear section thereof.
In order to improve a balance at the time of working, a power shovel includes a weight called a counterweight at the rear part of the upper rotation body (for example, Patent Document 1). Conventionally, a technique that a counterweight has a detachable structure capable of being attached/detached according to a necessity is also publicly known. Further, a counterweight integrated with a vehicle body frame, and the like is also used.
Patent Document 1: Japanese Patent No. 3732480